As energy prices are increasing due to depletion of fossil fuels and interest in environmental pollution is escalating, the demand for environmentally-friendly alternative energy sources is bound to play an increasing role in the future. Thus, research into techniques for generating various powers, such as nuclear energy, solar energy, wind energy, and tidal power, is underway, and power storage devices for more efficient use of the generated energy are also drawing much attention.
In particular, the demand for batteries as energy sources is rapidly increasing as mobile device technology continues to develop and the demand for the mobile devices continues to increase. In recent years, the use of secondary batteries as a power source of electric vehicles (EV) and hybrid electric vehicles (HEV) has been realized, and the market for lithium secondary batteries continues to expand to applications such as auxiliary power suppliers through smart-grid technology. Accordingly, much research on batteries satisfying various needs has been carried out.
Typically, small-sized mobile devices use one or several battery cells for each device. On the other hand, middle or large-sized devices, such as vehicles, use a middle or large-sized battery module including a plurality of battery cells electrically connected to each other because high output and large capacity are necessary for the middle or large-sized devices.
Preferably, the middle or large-sized battery module is manufactured so as to have as small a size and weight as possible. For this reason, a prismatic battery or a pouch-shaped battery, which can be stacked with high integration and has a small weight to capacity ratio, is usually used as a battery cell of the middle or large-sized battery module. In particular, much interest is currently focused on the pouch-shaped battery, which uses an aluminum laminate sheet as a sheathing member, because the weight of the pouch-shaped battery is small, and it is easy to modify the shape of the pouch-shaped battery.
Battery cells constituting the middle or large-sized battery module may be secondary batteries which can be charged and discharged. During charge and discharge of such a high-output, large-capacity secondary battery, a larger amount of heat is generated from the battery. In particular, the laminate sheet of each pouch-shaped battery widely used in the battery module has a polymer material exhibiting low thermal conductivity coated on the surface thereof with the result that it is difficult to effectively lower overall temperature of the battery cells.
In addition, if the heat, generated from the battery module during charge and discharge of the battery module, is not effectively removed from the battery module, the heat accumulates in the battery module with the result that deterioration of the battery module is accelerated. According to circumstances, the battery module may catch fire or explode. For this reason, the middle or large-sized battery module or a middle or large-sized battery pack for vehicles, which is a high-output, large-capacity battery, including a plurality of middle or large-sized battery modules needs a cooling system to cool battery cells mounted therein.
Each battery module mounted in the middle or large-sized battery pack is generally manufactured by stacking a plurality of battery cells with high integration. In this case, the battery cells are stacked in a state in which the battery cells are arranged at predetermined intervals such that heat generated during charge and discharge of the battery cells can be removed. For example, the battery cells may be sequentially stacked in a state in which the battery cells are arranged at predetermined intervals without using an additional member. Alternatively, in a case in which the battery cells have low mechanical strength, one or more battery cells may be mounted in a frame member, such as a cartridge, to constitute a unit module, and a plurality of unit modules may be stacked to constitute a battery module.
FIG. 1 is an exploded view schematically showing the structure of unit modules constituting a conventional battery module, and FIG. 2 is a typical view schematically showing the structure of the battery module of FIG. 1 when viewed from the front of the battery module.
Referring to FIGS. 1 and 2, a battery module 100 is configured to have a structure in which a plurality of unit modules 110 is arranged in tight contact with one another. The battery module 100 is generally formed in a hexahedral shape.
Each of the unit modules 110 is configured such that two plate-shaped battery cells 131 and 132 face each other while contacting each other in a state in which a frame member 12 is disposed between the battery cells 131 and 132. A cooling member 140 is interposed between the two plate-shaped battery cells 131 and 132, specifically between the frame member 120 and the battery cell 131 and/or between the frame member 120 and the battery cell 132. Cover members 151 and 152 are coupled to the front and the rear of the battery module 100, respectively.
The cooling member 140 generally has a structure corresponding to the shape and the size of the plate-shaped battery cells 131 and 132. Specifically, the cooling member 140 includes a plate-shaped cooling fin 141 having a shape and a size corresponding to those of the battery cells 131 and 132 and a coolant conduit 142 disposed along the outer edge of the cooling fin 141. The coolant conduit 142 has a hollow structure.
The coolant conduit 142 includes a coolant inlet port 143 and a coolant outlet port 144 provided at a central region of the lower side of the cooling fin 141. The coolant inlet port 143 and the coolant outlet port 144 of the coolant conduit 142 are coupled respectively to cooling manifolds 161 and 162 located at the lower part of the battery module 100 in a communicating fashion.
The battery module 100 is generally formed in a rectangular shape when viewed from the front of the battery module 100. The battery module 100 is provided at corners thereof with fastening parts 101, 102, 103, and 104 for coupling the unit modules.
The cooling manifolds 161 and 162 are coupled to the lower part of the battery module 100. Specifically, the cooling manifolds 161 and 162 are coupled respectively to the coolant inlet port and the coolant outlet port of the coolant conduit 142 formed at the central region of the lower side of the cooling fin in a communicating fashion.
At this time, the coolant inlet port 143 and the coolant outlet port 144 are located adjacent to an approximately central region of the lower part of the battery module 100. When a coolant introduced through the cooling manifold 161 passes through the coolant inlet port 143 of the coolant conduit 142 and is then discharged through the cooling manifold 162 connected to the coolant outlet port 144, therefore, the coolant is circulated along the outer edge of the cooling fin 141, thereby maximizing cooling efficiency of the battery module 100.
In the conventional battery module 100 with the above-stated construction, the coolant conduit 142 of the cooling member 140, which is provided along the outer edge of the cooling fin 141, is bent at six points 142a, 142b, 142c, 142d, 142e, and 142f As a result, manufacturing cost of the cooling member 140 is increased. Furthermore, the pressure of the coolant along the outer edge of the cooling fin 141 through the coolant conduit 142 is lowered due to the bent structures with the result that the cooling efficiency of the battery module 100 may be lowered.
In addition, the cooling manifolds 161 and 162 are coupled to the central region of the lower part of the battery module 100 at which the coolant inlet port 143 and the coolant outlet port 144 are located. At the time of manufacturing the battery module, therefore, it is necessary to individually couple the cooling manifolds 161 and 162 to the coolant inlet port 143 and the coolant outlet port 144 of the cooling member 140 of each of the unit modules 110 with the result that manufacturing time of the battery module 100 is increased. Furthermore, at the time of manufacturing a battery pack including two or more battery modules 100, the cooling manifolds 161 and 162 are located between each of the battery modules 100 and a tray assembly. As a result, it is not possible to directly inspect a coupling state between the cooling manifolds 161 and 162 and the coolant inlet port 143 and the coolant outlet port 144 with the naked eye, whereby a product defect rate is increased.
Therefore, there is a high necessity for technology that is capable of fundamentally solving the above problems.